3 Minutes of Exercise and Two Fasts a Week: Is This the Future of Fitness?

British doctor Michael Mosley takes a streamlined approach to workouts and food in PBS specials

Credit: Courtesy of Jenna Caldwell-WeilerThe Truth About Exercise with Michael Mosley will air on PBS on April 10

More than a year ago, Dr. Michael Mosley got some scary news. His doctor told him that his blood glucose level was high, putting him at risk for diabetes, and that his level of insulin-like growth factor-1, or IGF1, was elevated, raising the chances he'd contract prostate or colorectal cancer. So Mosley did what many of us would: He tried to find the most effective way to ensure a healthy future while making as few changes to his life as possible.

What he discovered is the basis of Eat, Fast and Live Longer, a series of three TV specials created for the BBC and airing this month on PBS. He also wrote The Fast Diet, which has become a No. 1 best-selling book in the United Kingdom.

The series chronicles Mosley's journey to consult experts in diet, exercise and emerging genetic approaches to health. As he now sees it, much of what we thought we knew about food and fitness is wrong.

5 Days to Feed, 2 Days to Fast

Mosley, 55, says the prominent diet researcher Dr. Luigi Fontana, a professor of medicine at Washington University in St. Louis, told him he needed to immediately address his elevated glucose and IGF1 levels. "If I didn't change my ways," Mosley says, "within a decade I'd probably be on six or seven drugs, like the average American in their mid-60s. It was a bit of a wake-up call."

He began to reshape his eating habits through intermittent fasting. There are several approaches to the regimen, but in what has become the most popular form, known as the 5:2 diet, people eat normally (about 2,200 to 2,400 calories a day for men; 1,600 to 1,800 per day for women) five days a week — in some studies, participants have been asked to follow the Mediterranean diet on their "feed" days — and consume only a quarter of their usual calorie intake the other two (non-consecutive) days.

Fontana, who also practices intermittent fasting, reports the diet can lower IGF1 levels, among other benefits. Similar studies of women, led by Dr. Michelle Harvie of Manchester University in England, have found that subjects on a 5:2 regimen lose more fat and are more likely to stick with the regimen than those asked to follow the Mediterranean diet full time. That's significant, Harvie says, because when women can cut their body weight by 5 percent it lowers their risk of breast cancer by as much as 40 percent.

"We obviously need more human trials, but it's the beginning of something hopefully very interesting," says Mosley, understating the frenzy his book has caused in the United Kingdom, where his frequent appearances on the BBC have made him what The New York Times calls "the Sanjay Gupta of Britain."

Mosley says intermittent fasting helped him drop 19 pounds in nine weeks, from 187 to 168 pounds. On the two fast days, male dieters aim to eat about 600 calories (women: 500), the equivalent of two eggs with a piece of toast and berries for breakfast, plus steamed fish and vegetables for dinner. (Fasters drink water throughout the day.)

The author says he's feeling better since he lost weight and that his blood glucose and cholesterol levels have dropped. But he acknowledges that the diet is not for everyone — diabetics, pregnant or breastfeeding women or anyone with a history of eating disorders should avoid it. Fasting also has critics, who are skeptical of the amount of research into its long-term benefits and an individual's ability to stay with it.

"No diet is ever going to work for everyone," Mosley says. "There's a dropout rate in the trials, but we also know that's true of standard diets. The big question is: Are people more likely to stay on this than a standard diet? Initial indications are yes."

Three Minutes of Exertion

Mosley took a similar approach to overhauling his fitness. "We all know we should exercise," he says, "but people find it hard to persuade themselves to go out and do it. So I asked: What's the minimum amount of time you need to get the benefits?"

Turns out, three minutes a week — if you have the right genetic makeup.

Again drawing on research from both the United States and Europe, Mosley focused his attention on studies of high-intensity training (HIT), exhausting but relatively brief and infrequent exercise sessions.

Before beginning any fitness routine, Mosley says, "It would be interesting to know if you'll benefit a lot, a little or none." He cites research showing that as much as 20 percent of the population experience no increase in aerobic fitness — a measure of how efficiently your heart and lungs transport oxygen throughout your body — no matter their exercise regimen. (An additional 15 percent are considered to be "super-responders," able to achieve major improvements in aerobic fitness through exercise.) Mosley took a new genetic test not yet available to the public and discovered he could gain from aerobic exercise, then began his high-intensity training.

Research conducted in Europe and elsewhere has found that a high-intensity training regimen improved aerobic fitness as well as lengthier gym sessions did. It's also been shown to decrease insulin resistance, reducing the chance of contracting metabolic syndrome, which can put you at higher risk for diabetes or heart disease.

Mosley's high-intensity training sessions, which took place on an exercise bike, were fairly simple: A couple of minutes warming up at moderate speed, followed by 20 seconds of high intensity, as fast as he could go. He then repeated the cycle two more times, for a total high-intensity workout of one minute. By following the same routine three times a week, he recorded three minutes of high-intensity training. "Those 20-second bursts seem to do the trick," he says, adding that he continues to practice a form of this training when biking home, uphill, from his office. "It's great to incorporate it into your life," he jokes, "but the exercise bike is probably a gentler way to go."

Mosley emphasizes that while high-intensity training can be a substitute for longer, more frequent gym sessions, it does not diminish anyone's need to be as mobile as possible to compensate for the deleterious effect of sitting. "The chair is a killer," one researcher told Mosley, who adds, "If you sit at a computer for 10 hours a day barely moving and then go to the gym, it's not enough."

The genetic test he took, Mosley believes, is just one herald of a coming "era of personalized fitness." In the near future, he says, genetic testing will tell us not only if we can benefit from exercise, but if we are prone to particular diet risks, like hypertension from high salt intake. Personalized warnings, he suggests, may someday replace public health campaigns. "It's different being told generally that it would probably be a good thing to cut back on salt," he says, "than being told, 'It's you.'"

The Less Change the Better

Mosley says his goal is to help people get healthier through manageable lifestyle changes they can follow without completely disrupting their daily lives. "We are creatures of habit," he says, "and it's incredibly difficult to change our routines and do something completely different. I recognize that about myself.

"The idea should be to create a cornerstone habit," he says, "one thing that you can change and then other changes will flow from it. When I started looking at intermittent fasting, I saw that it was psychologically attractive because you don't have to change all of your eating habits forever, just a few days a week."